The question as to how many things, whether objects or ideas, can be attended to at the same time, has aroused considerable discussion. Most people think that they are attending to several things, if not to many, at the same second of consciousness. Experiments show that if four or five unrelated objects, words, or letters be shown to adults for less than one quarter of a second, they can be apprehended, but the probability is that they are photographed, so to speak, on the eye and counted afterwards. It is the general belief of psychologists at present that the mind attends to only one thing at a time, that only one idea or object can occupy the focal point in consciousness. The apparent contradiction between ordinary experience and psychological experience along this line is due to three facts which are often overlooked. In the first place, the complexity of the idea or thing that can be attended to as a unit varies tremendously. Differences in people account for part of this variation, but training and experience account for still more. Our ideas become more and more complex as experience and familiarity build them up. Qualities which to a little child demand separate acts of attention are with the adult merged into his perception of the object. Just as simple words, although composed of separate letters, are perceived as units, so with training, more complex units may be found which can be attended to as wholes. So (to the ignorant or the uninstructed) what is apparently attending to more than one thing at a time may be explained by the complexity of the unit which is receiving the attention. In the second place _doing_ more than one thing at a time does not imply attending to more than one thing at a time. An activity which is habitual or mechanical does not need attention, but can be carried on by the control exercised by the fringe of consciousness. Attention may be needed to start the activity or if a difficulty of any kind should arise, but that is all. For the rest of the time it can be devoted to anything else. The great speed with which attention can flash from one thing to another and back again must be taken into consideration in all this discussion. So far as attention goes, one can _do_ as many things at a time as he can make mechanical plus one unfamiliar one. Thus a woman can rock the baby's cradle, croon a lullaby, knit, and at the same time be thinking of illustrations for her paper at the Woman's Club, because only one of these activities needs attention. When no one of the activities is automatic and the individual must depend on the rapid change of attention from one to the other to keep them going, the results obtained are likely to be poor and the fatigue is great. The attempt to take notes while listening to a lecture is of this order, and hence the unsatisfactoriness of the results.